EP0381266A1

EP0381266A1 - Longitudinal magnetic tape recording system, magnetic tape apparatus and magnetic head means.

Info

Publication number: EP0381266A1
Application number: EP90200172A
Authority: EP
Inventors: Johannes Cornelius Antonius Muller; Abraham Hoogendoorn
Original assignee: Philips Gloeilampenfabrieken NV; Koninklijke Philips Electronics NV
Current assignee: Koninklijke Philips NV
Priority date: 1989-01-30
Filing date: 1990-01-24
Publication date: 1990-08-08
Anticipated expiration: 2010-01-24
Also published as: JPH02232802A; DE69027132D1; ES2088954T3; CA2008650A1; ATE138754T1; EP0381266B1; DE69027132T2; AR246632A1; AU4885790A; RU2063069C1; CN1045309A; MY105796A; HU205998B; HU900367D0; PL165830B1; CZ526790A3; CS39590A2; US5831798A; PT92970A; NL8901712A

Abstract

A longitudinal magnetic-tape system comprises cassettes (4) and analog recorders (1) comprising analog magnetic heads (15) with which analog information can be recorded in and/or read from longitudinal tracks on a magnetic tape (5) accommodated in the cassette (4). The system also comprises digital recorders (2) comprising digital magnetic heads (25) with which digital information can be recorded in and/or read from longitudinal tracks on said magnetic tape accommodated in said cassette, which digital recorders (2) are compatible with said analog recorders (1) to such an extent that the analog information recorded on a magnetic tape (5) in the cassette (4) of the system by an analog recorder (1) belonging to the system can at least be read with magnetic-head means (25) of the digital recorders (2) belonging to the system.

Description

The invention relates to a longitudinal magnetic tape recording system comprising an apparatus and a cassette having a housing, which housing comprises two substantially parallel main walls and a plurality of transverse walls and accommodates two reels and the magnetic tape, which magnetic tape is wound at least partly on one of the reels and extends partly between the two reels across an opening formed in one of the transverse walls of the housing, which apparatus is constructed to cooperate with the cassette in a first position of the cassette and in a second position of the cassette which second position is rotated through at least substantially 180^o relative to the first position about an axis which extends parallel to the main walls perpendicularly to the transverse wall formed with the opening and through the centre of said transverse wall, which apparatus comprises magnetic-head means including at least one magnetic-head for reading and/or writing information in analog form on the magnetic tape, and tape-transport means for the transport of the magnetic tape past the magnetic-head means with a speed of transport.
Such a system is generally known in the form of the standard Compact Cassette system comprising apparatuses for reading and/or writing information generally in the form of music, in analog form in longitudinal tracks on a magnetic tape. In this sytem the cassette is reversible, so that after reversal of the cassette recording and/or reproduction of the information on/from the magnetic tape can be continued without prior rewinding of the tape or replacement of the cassette. The information is situated in longitudinal tracks on the magnetic tape or is recorded on the magnetic tape in the longitudinal direction. This standard system is defined in IEC publication 94.
A disadvantage of this system is that the signal-to-noise ratio and the quality of the recorded signal itself are noticeably degraded in comparison with the original source signal.
The music quality is inferior to that of the Compact Disc system, even in the case of the best equipment and magnetic-tape cassettes of the Compact Cassette system. In order to upgrade the quality the prior art system has been improved in many respects, such as for example by the use of automatic azimuth control and a variety of noise reduction systems. These improvements make the equipment far more expensive and,in spite of this a quality comparable to that of the Compact Disc cannot be attained. As a result of this, high-quality apparatuses of the Compact Cassette system are far more expensive than simple Compact Disc apparatuses, although their quality is distinctly inferior.
However, a huge number of Compact Cassettes and associated recorders are in use in the market. It is estimated that there are approximately one billion recorders and that the number of cassettes is a multiple thereof.
A system having quality similar to that of the Compact Disc system is for example the R-DAT system. The disadvantage of this system is that it requires an entirely new magnetic tape cassette and magnetic tape apparatus with a helical-scan deck. This results in more expensive cassettes and cassette decks and the multitude of Compact Cassettes which are in use cannot be employed in conjunction with this system. The principal disadvantage of such new systems resides in the fact that the market is diffucult to penetrate because these systems are wholly incompatible with the well-known Compact Cassette system. This incompatibility means a larger expenditure for the consumer and huge and insecure investments for the manufacturers and the software industry.
It is an object of the invention to construct a system in such a way that the signal-to-noise ratio and the signal itself are improved considerably with a minimal adaptation of the system, enabling a gradual marking penetration to be achieved.
To this end the invention is characterized in that the system comprises at least two types of apparatus, i.e. in addition to an apparatus of a first type, being said apparatus comprising magnetic-head means of a first type, the system comprises a further apparatus of a second type, which is constructed to cooperate with said cassette and which comprises magnetic-head means of a second type, comprising a magnetic head of a second type, the magnetic-head means of the second type being consturcted to read and/or write information in digital form in longitudinal tracks on the magnetic tape. By recording and reading the information in digital form the tape noise has no influence on the signal and, moreover, this provides an extended frequency range, so that the recorded signal itself has also improved. The novel system does not require a new type of cassette, it is for example possible to use the current Compact Cassettes. Moreover, an apparatus of the second type need not differ much from an apparatus of the first type, apart from the magnetic head means and some electronic devices. This enables a considerably improved new system to be obtained with minimum adaptations to a prior-art system.
An embodiment of the system in accordance with the invention is characterized in that the magnetic head means of the second type are constructed also to at least read information from the recorded on the magnetic tape in analog form. Thus, the system in accordance with the invention is compatible with the prior art system at least in respect of the reproduction of information recorded on the magnetic tape in analog form. Therefore, prerecorded analog cassettes can always be played back on apparatuses of the second type so that it is not necessary for the consumer to have an apparatus of the first type in addition to the novel apparatus of the second type.
A further embodiment of the system in accordance with the invention is characterized in that the magnetic-head of the second type comprises a plurality of at least substantially parallel transmission gaps which are disposed substantially in line with one another and which are formed in a head face, which gaps form at least one pattern for reading and/or writing information on the magnetic tape in one tape transport direction, the transmission gaps of the pattern being situated in the head face in such a way that in the case of mirror-imaging relative to a central line of the head face perpendicular to the transmission gaps a mirror image of a transmission gap of the pattern is formed at least substantially between two adjacent transmission gaps of the pattern. The inter-gap distances are then such that during manufacture hardly any problems will occur and the heads can be manufactured with simple technologies, for example by means of the method as described in United States Patent Specification 3,593,414 (PHN 3398, herewith incorporated by reference). If there is some overlap between the transmission gaps and the mirror images this need not present any problem. In fact, this overlap means that during operation in the opposite direction of tape transport the transmission gap also partly overlaps the track written during operation in the other direction of tape transport. During reading this will not give rise to any significant problem, while during recording a part of the track already recorded will be overwritten.
Another embodiment of the system in accordance with the invention is characterized in that the magnetic head of the second type comprises a plurality of at least substantially parallel transmission gaps formed in a head face substantially in line with one another, which gaps form at least one pattern for reading and/or writing information on the magnetic tape in a direction of tape transport, the pattern being situated in the heat face, wholly at one side of a central line of the head face perpendicular to the transmission gaps. An advantage of this is that an analog track can be read with a plurality of gaps, so that signal losses are smaller than in the case of reading by means of only one gap. A further advantage is that the other side ofthe head face can be used for an analog part.
A further embodiment of the system in accordance with the invention is characterized in that the transmission gaps of the magnetic head of the second type form a further pattern for reading and/or writing information on the magnetic tape in another direction of tape transport opposite to said direction of tape transport. An advantage of this is that the magnetic head need not be reversed or set to another position when an auto-reverse system is used.
Still another embodiment of the system in accordance with the invention, in which the magnetic head of the first type comprises a plurality of parallel transmission gaps formed in a head face in line with one another, which gaps form at least one pattern for reading and/or writing information in an analog form on the magnetic tape in one direction of tape transport, the pattern being situated inthe head face, wholly at one side of a central line of the head face perpendicular to the transmission gaps in the head face, is characterized in that when the head face of the magnetic head of the second type is projected onto the head face of the magnetic head of the first type, at least a projection of a transmission gap of the magnetic head of the second type is obtained on every transmission gap of the magnetic head of the first type. This enables information recorded on a magnetic tape in analog form by a magnetic head of the first type to be read with a magnetic head of the second type.
Yet another embodiment of the system in accordance with the invention is characterized in that both types of apparatus have thesame speed of tape transport. When the same or substantially the same cassettes are employed this results in equal playing times both for the known apparatuses of the first type and for the novel apparatuses of the second type.
Still another embodiment of the system in accordance with the invention is characterized in that the apparatus of the second type comprises means for compressing and/or expanding information in digital form. The information in digital form should be expanded or compressed in order to enable the information to be reproduced from or recorded in a reduced number of tracks of the magnetic tape for the given speed of tape transport. The number of tracks is then reduced relative to the number of tracks to be employed without the use ofexpansion and compression means. This data compression and expansion is also of significance in view of the requirements to be imposed on a magnetic head of the second type. This is because the number of gaps of the magnetic head by which said data is to be processed depends on the data reduction and the write frequency. In the absence of data reduction approximately 20 transmission gaps would be needed to record the information at the customary recording frequency. The amount to be written per unit of time can be reduced by the use of data compression, so that a substantially smaller number of transmission gaps can be used at the same recording frequency.
In order to achieve that only one transport speed is required for reading information a further embodiment is characterized in that the apparatuses of the second type are constructed to read information recorded on the magnetic tape in digital form and in analog form and in that the information in digital form is arranged in a plurality of tracks and is encoded in such a way that the information in digital form can be read with the same tape-transport speed as used for reading information in analog form. The number of tracks with which the information in digital form is recorded on the magnetic tape and/or is read from the magnetic tape is limited in view of the problems encountered in the manufacture of magnetic heads for reading and/or writing information in a larger number of tracks. In order to enable the information in digital form to be read with the same tape-transport speed as used for reading information in analog form with said limited number of tracks the information should be encoded in such a way that the same amount of data is obtained as in the case of the data compression described above.
Yet a further embodiment of the system in accordance with the invention is characterized in that the pattern of transmission gaps of the magnetic head of the second type comprises nine gaps, of which one gap constitutes an auxiliary gap for reading and/or writing auxiliary information and the other eight gaps form main gaps for reading and/or writing the information. When eight gaps are used the amount of information is found to be adequate in order to achieve that after expansion during reproduction hardly any differences can be detected in comparison with the original signal. Moreover, the auxiliary gap enables information, relating to for example the residual time available on and the elapsed time of the tape and/or data relating to the information on the tape, to be read and/or to be recorded.
The invention further relates to a magnetic tape apparatus of the second type for use in a system in accordance with the invention.
An embodiment of such a magnetic tape apparatus is characterized in that the magnetic head means of the second type comprise a magnetic head of the second type, which magnetic head is constructed to read both information in analog form and information in digital form, and which magnetic head means comprise a further magnetic head of the second type for recording information at least in digital form. The use of a separate read head and a separate write head has the advantage that the heads can be manufactured more simply.
A further embodiment of the magnetic tape apparatus in accordance with the invention is characterized in that the magnetic head of the second type is constructed to read and write information in digital form and at least to read information in analog form. This has the advantage that no alignment of the read and write gaps relative to each other is needed. Another advantage of this is that the contact area between the magnetic head and the magnetic tape can be smaller, so that an effective tape-head contact can be achieved more simply.
A further embodiment of the magnetic tape apparatus in accordance with the invention is characterized in that the magnetic head, which is constructed at least to read both information in analog form and information in digital form, comprises a plurality of parallel transmission gaps disposed in line with each other in a head face, which gaps are arranged in two sub-patterns, the first sub-pattern corresponding to a pattern of transmission gaps for at least reading information in digital form on the magnetic tape in one direction of tape transport, and the second sub-pattern corresponding to a patternof transmission gaps for at least reading information in analog form on the magnetic tape in one direction of tape transport. This magnetic head has the advantage that the analog signal on the magnetic tape can be read wit less losses than in the case of magnetic heads which read the analog signal by means of one of the gaps of the gap pattern for reading and/or writing information in digital form, because the transmission gaps for reading information in analog form have substanially the same width as the analog information tracks on the magnetic tape whilst the transmission gaps for reading digital information are much narrower.
An embodiment of the magnetic tape apparatus in accordance with the invention is characterized in that at least one magnetic head of the second type is rotatable through at least substantially 180^o about an axis perpendicular to the head face. This enables auto-reverse operation to be achieved with apparatuses of the second type, in the same way as in the prior-art apparatuses of the first type, as described for example in European Patent 0,120,518 B1 (PHN 10.602, herewith incorporated by reference), so that no new adaptations are needed.
Another embodiment of the magnetic-tape apparatus in accordance with the invention is characterized in that at least one magnetic head of the second type is movable over a distance in a direction at least substantially parallel to the transmission gaps, which distance is at least substantially equal to half the distance between the centres of two adjacent transmission gaps, to read and/or write information in digital form on the magnetic tape in the same tape transport direction. This is an advantage in the embodiment of the system, in which the distance between the transmission gaps of the magnetic head is at least equal to the width of a transmission gap. For auto-reverse operation the magnetic head need then not be rotated but that a small displacement being already adquate to reach the intermediate tracks.
The invention also relates to a magnetic head of the second type, for use in a magnetic-tape apparatus in accordance with the invention.
An embodiment of such a magnetic head is characterized in that the magnetic head comprises eleven parallel transmission gaps of different dimensions, which gaps are disposed in line with one another in a head face, which head face is bisected by a central line perpendicular to the transmission gaps, nine of said transmission gaps being configured to read and/or write information in digital form and two further of said transmission gaps being configured to at least read information in analog form, nine transmission gaps for reading and/or writing information in digital form being provided in one half of the head face, the transmission gap which is remotest from the central line being configured to read and/or write auxiliary information in digital form, and the two transmission gaps for at least reading information in analog form being provided in the other half of the head face. This enables both information in digital form and in analog form to be read.
The two transmission gaps for at least reading information in analog form have the same dimensions as the transmission gaps of the well-known magnetic heads as used in the standard Compact Cassette system. This enables information in analog form recorded on a magnetic tape in accordance with the Compact Cassette system to be read in an optimum manner. For reading and writing informtion in digital form eight transmission gaps are provided. The number of transmission gaps is selected in such as way that for the given tape-transport speed and data coding the information can be written on or read from the magnetic tape. The transmission gap for reading and writing auxiliary information is remote from the central line of the head face. A further transmission gap for reading and/or writing auxiliary information may be provided in the half of the head face where the two transmission gaps for at least reading information in analog form are situated, in order to insert auxiliary information during analog recording in accordance with the Compact Cassette standard. Both during reading information in analog form and during reading or writing informtion in didigtal form auto-reverse operation is possible by turning the magnetic head through 180^o.
In order to achieve that the magnetic head need not be displaced for auto-reverse operation a further embodiment of the magnetic head is characterized in that the magnetic head comprises two groups of parallel transmission gaps which are disposed in line with each other in a head face which is bisected by a central line perpendicular to the transmission gaps, which groups each comprise two subgroups, being a first subgroup having transmission gaps in one half of the head face, for reading and/or writing information in digital form and a second subgroups having transmission gaps in the other half of the head face for at least reading information in analog form, a first subgroup of one of the groups and a second subgroup of the other group of transmission gaps being provided in each half of the head face.
Embodiments of the invention will now be described in more detail, by way of example, with reference to the accompanying drawings. In the drawings:

Fig. 1 shows a magnetic-tape apparatus of the first type,
Fig. 2 shows an example of a cassette,
Fig. 3 shows an embodiment of a magnetic tape apparatus of the second type,
Fig. 4 shows another embodiment of a magnetic tape apparatus of the second type,
Fig. 5 shows an embodiment of a magnetic head of the first type,
Fig. 6 shows a first embodiment of a magnetic head of the second type,
Fig. 7 shows a second embodiment of a magnetic head of the second type,
Fig. 7a shows how the transmission gaps and their mirror images are disposed the case of a mirror-imaging relative to the central line of the magnetic head of the second type shown in Fig. 7,
Fig. 7b shows the projection of the transmission gaps of the second embodiment of the magnetic head of the second type on the transmission gaps of a magnetic head of the first type,
Fig. 8a shows a third embodiment of a magnetic head of the second type,
Fig. 8b shows another embodiment of the magnetic head shown in Fig. 8a,
Fig. 9 shows two magnetic heads of the second type constructed for use in the apparatus shown in Fig. 4,
Fig. 10 shows a further embodiment of a magnetic head of the second type provided with two patterns of transmission gaps, and
Fig. 11 shows yet another magnetic head of the second type having two patterns of transmission gaps.

An embodiment of a system in accordance with the invention comprises a magnetic-tape apparatus of the first type shown in Fig. 1, a magnetic tape apparatus of the second type shown in Fig. 3,and a cassette in the form of a well-known audio cassette 4 (a "Compact Cassette" as standardized in IEC publication no. 94-7) shown in Fig. 2.
The magnetic-tape apparatus 1 of the first type shown in Fig. 1 is constructed to read and/or write information in analog form on a magnetic tape accommodated in the cassette 4. For this purpose the apparatus 1 comprises tape-transport means, comprising a capstan/pressure roller combination 10, drive spindles 11 and 12, and magnetic head means 13, in the present embodiment represented as an erase head 14 and a magnetic head 15 of the first type for reading and/or writing information in analog form. This apparatus is a cassette recorder of a generally known type, so that for the sake of brevity no further details will be given.
Fig. 2 shows the cassette 4 in greater detail. The cassette comprises a housing having two main walls 41 and 42 and four transverse walls 43, 44, 45 and 46. The housing accommodates the magnetic tape 5, which is wound on reels 47 and 48 and which extends partly across an opening 49 formed in the transverse wall 43. The cassette 4 is constructed to cooperate with the apparatus 1 in a first position as shown in Fig. 1 and in a second position obtained by turning the cassette 4 through 180^o about an axis of rotation 40 shown in Fig. 2.
The magnetic tape apparatus 2 of the second type shown in Fig. 3 is also constructed to cooperate with the head 4. This apparatus 2 comprises a capstan/pressure roller combination 20 and drive spindles 21 and 22. The magnetic head means 23 comprise an erase head 24 and a magnetic head 25 of the second type. The magnetic head 25 is constructed to read and write information in digital form and to read information in analog form. For reading and writing information in digital form the apparatus 2 further comprises compression and expansion means 27. These means are needed to write the information in digital form of the magnetic tape or to read said information from the magnetic tape in a limited number of information tracks with the same tape-transport speed as in the apparatus 1 of the first type.
Fig. 4 shows another embodiment of the apparatus 3 of the second type. This apparatus again comprises a capstan/pressure roller combination 30, drive spindles 31 and 32, compression and expansion means 37, and magnetic-head means 33. The magnetic head means 33 comprise an erase head 34 and two magnetic-heads of the second type, i.e. a magnetic head 35 for reading information in analog or in digital form, and a magnetic head 36 for recording information in digital form.
The apparatuses 2 and 3 of the second type shown in Figs. 3 and 4 differ only slightly from the apparatus 1 of the first type. The differences mainly reside in different magnetic-head means 23, 33 and the presence of digital electronic circuits such as compression and expansion means 27, 37 and the necessary analog/digital and digital/analog converters.
Fig. 5 shows a prior-art magnetic head 15 of the first type, which has two transmission gaps 18 disposed in one half of the head face 16 which is bisected by a central line 17. This magnetic head 15 is configured to read and write information in analog form.
Figs. 6, 7, 82 and 86 show embodiments of magnetic heads 25, 28 and 29 of the second type, which are constructed for use in the apparatus 2 of the second type shown in Fig. 3. In the magnetic head 25 shown in Fig. 6 the transmission gaps 62 and 63 are also disposed in one half of a head face 60 which is bisected by a central line 61. In the magnetic head 28 shown in Fig. 7 the transmission gaps 72 and 73 are divided over the entire width of the head face 70 in such a way that in the case of mirror-imaging relative to the central line 71 the mirror images 74 of the transmission gaps 72, 73 will be situated between the transmission gaps 72, 73 themselves without any overlap, see Fig. 7a. In addition to the track pattern of transmission gaps as shown in Fig. 6, the embodiment of the magnetic head 29a of the second type shown in Fig. 82 has a further track pattern comprising two transmission gaps 84 for reading information in analog form. This magnetic head 29a may be constructed from two halves. The compound magnetic head 29a can be obtained by combining one half of the magnetic head 25 shown in Fig. 6 with one half of the prior-art magnetic head 15 shown in Fig. 5. Alternatively, the magnetic head 29a can also be constructed as an integral unit by integrating the transmission gaps 82, 83 and 84 in one head.
Fig. 8b shows another modification of a compound magnetic head 29b. In this modification the prior-art magnetic head 15 shown in Fig. 5 and the magnetic head 25 shown in Fig. 6 are juxtaposed. This costruction can be manufactured more simply than that shown in Fig. 8a. The magnetic head 29b has two head faces 86a and 86b. In one half situated at one side of the central line 87 the head face 86a has main gaps 89 and an auxiliary gap 89a for digitally reading and writing information. In the other half at the other side of the central line 87 the head face 86b has the transmission gaps 88 for at least reading analog information. The auxiliary transmission gaps 63, 73, 83 and 89a are constructed to read and write auxiliary information. This auxiliary information may include for example data on the information recorded on the tape or data on the position of the head relative to the beginning or end of the tape. The main transmission gaps 62, 72, 82 and 89 are configured to read and write information in digital form. In addition, the gaps 62 and 72 are configured to read information in analog form. When the head face 70 of the magnetic head 28 of the second type is projected onto the head face 16 of the magnetic head 15 of the first type at least one projection 100 of a transmission gap of the magnetic head 28 is situated on every transmission gap 18 of the magnetic head 15, see Fig. 7b. Preferably, a projection 100 of a transmission gap of the magnetic head 28 of the second type is situated on the centre of each transmission gap 18 of the magnetic head 15 of the first type, as is illustrated in Fig. 7b. For auto-reverse operation the magnetic heads 25, 28 and 29 can be rotated through 180^o about the axis 101 to cooperate with the track pattern of the information on the magnetic tape for the purpose of reading and/or writing in the reverse direction of tape transport, see Fig. 7a. The magnetic head 28 shown in Fig. 7 can be moved over a distance 102 for the purpose of auto-reverse operation, see Fig. 7a. This distance 102 should be substantially equal to half the distance 103 between the centres of two adjacent transmission gaps 72.
Fig. 9 shows a combination of two magnetic heads 35 and 36 of the second type suitable for use in the apparatus shown in Fig. 4. The magnetic head 35 is configured both to read information in digital form by means of the transmission gaps 92 and 93 and to read information in analog form by means of the transmission gaps 94. The magnetic head 36 is constructed to write information in digital form by means of the gaps 96 and 97. The gaps 93 and 97 constitute the auxiliary transmission gaps and the gaps 92 and 96 constitute the main transmission gaps. The eight main transmission gaps 92, 96 and one auxiliary transmission gap 93, 97 are situated in one half of the head face 90 which is bisected by the central line 91 and the transmission gaps 94 for the information in analog form are situated in the other half.
Fig. 10 shows a magnetic head 105 of the second type, which is formed with two patterns of transmission gaps. One pattern comprising the auxiliary transmission gap 109a and the main transmission gap 108a, is adapted to cooperate with the magnetic tape in one direction of tape transport. The other pattern, comprising the auxiliary transmission gap 109b and the main transmission gaps 108b, is adapted to cooperate with the magnetic tape in another direction of tape transport, opposite to the said direction of tape transport. As a result of this, it is not necessary to rotate or to displace the head in the case of auto-reverse operation. The operation of the magnetic head can be adapted to tape transport in the opposite direction by deactivating the operative pattern and by activating the other pattern.
The associated gaps of a pattern of the magnetic head 105 shown in Fig. 10 are all situated in one half of the head face 106, which is bisected by the central axis 107. Obviously it is also possible to juxtapose one gap of a pattern and a gap of the other pattern in order to obtain a magnetic head having two interdigitated gap patterns.
Fig. 11 shows a magnetic head 110 which is very suitable for auto-reverse operation, because the magnetic head need not be rotated or moved for this purpose. A central line 113 bisects the head face into two halves 111 and 112. Each half is provided with a first subgroup, 117 and 118 respectively, of transmission gaps for reading or writing information in digital form and with a second subgroup, 116 and 119 respectively, for at least reading information in analog form.
In the foregoing a number of embodiments have been described with reference to diagrammatic Figures merely by way of illustration. However, the invention is not limited to the embodiments described herein, numerous other embodiments which utilise the inventive principle in a way other than described, being possible within the scope of the invention as defined in the appended Claims, said principle beingthat a known system for a longitudinal analog recording is extended to obtain digital longitudinal recording by the addition of digital recorders. Moreover, such a system provides substantial advantages if use is made of the inventive principle of constructing digital recorders in such a way that they are compatible with the original recording system, at least in so far as they are adapted to at least play back cassettes with an analog recording.
For example, in contradistinction to the embodiments described herein, embodiments of the invention are possible in which the apparatuses are constructed only for the reproduction of digital and analog signals, for example car cassette players or portable cassette players or in which the apparatuses are capable both of analog and digital reading and recording. Moreover, it is possible to dispense with the erase head. By appropriately guiding and positioning the tape relative to the magnetic head the tracks already present can be overwritten almost completely with tracks containing new information to be recorded.

Claims

1. A longitudinal magnetic-tape recording system comprising an apparatus and a cassette having a housing, which housing comprises two substantially parallel main walls and a plurality of transverse walls, accommodates two reels and the magnetic tape, which magnetic tape is wound at least partly on one of the reels and extends partly between the two reels across an opening formed in one of the transverse walls of the housing, which apparatus is constructed to cooperate with the cassette in a first position of the cassette and in a second position of the cassette, which second position is rotated through at least substantially 180^o relative to the first position about an axis whichextends parallel to the main walls perpendicularly to the transverse wall formed with the opening and through the centre of said transverse wall, which apparatus comprises magnetic-head means including at least one magnetic head for reading and/or writig information in analog form on the magnetic tape, and tape-transport means for the transport of the magnetic tape past the magnetic-head means with a speed of transport, characterized in that the system comprises at least two types of apparatus, i.e. in addition to an apparatus of a first type, being said apparatus comprising magnetic-head means of a first type, the system comprises a further apparatus of a second type, which is constructed to cooperate with said cassette and which comprises magnetic-head means of a second type, comprising a magnetic head of a second type, the magnetic-head means of the second type being constructed to read and/or write information in digital form in longitudinal tracks on the magnetic tape.

2. A system as claimed in Claim 1, characterized in that the magnetic head means of the second type are constructed also, to at least read information in analog form from the magnetic tape.

3. A system as claimed in Claim 1 or 2, characterized in that the magnetic head of the second type comprises a plurality of at least substantially parallel transmission gaps which are disposed substantially in line with one another and which are formed in a head face, which gaps form at least one pattern for reading and/or writing information on the magnetic tape in one tape transport direction, the transmission gaps of the pattern being situated in the head face in such a way that in the case of mirror-imaging relative to a central line of the head face perpendicular to the transmission gaps a mirror image of a transmission gap of the pattern is formed at least substantially between two adjacent transmission gaps of the pattern.

4. A system as claimed in Claim 1 or 2, characterized in that the magnetic head of the second type comprises a plurality of at least substantially parallel transmission gaps formed in a head face substantially in line with one another, which gaps form at least one pattern for reading and/or writing information on the magnetic tape in direction of tape transport, the pattern being situated in the head facewholly at one side of a central line of the head face perpendicular to the transmission gaps.

5. A system as claimed in Claim 3 or 4, characterized in that the transmission gaps of the magnetic head of the second type form a further pattern for reading and/or writing information on the magnetic tape in another direction of tape transport, opposite to said directionof tape transport.

6. A system as claimed in Claim 3, 4 or 5, in which the magnetic head of the first type comprises a plurality of parallel transmission gaps formed in a head face in line with one another, which gaps form at least one pattern for reading and/or writing information in analog form on the magnetic tape in one direction of tape transport, the pattern being situated in the head face, wholly at one side of the central line of the head face perpendicular to the transmission gaps, characterized in that when the head face of the magnetic head of the second type is projected onto the head face of the magnetic head of the first type, at least a projection of a transmission gap of the magnetic head of the second type is obtained on every transmission gap of the magnetic head of the first type.

7. A system as claimed in any one of the preceding Claims, characterized in that both types of apparatus have the same speed of tape transport.

8. A system as claimed in Claim 7, characterized in that the apparatus of the second type comprises means for compressing and/or expanding information in digital form.

9. A system as claimed in Claims 7 and 8, characterized in that the apparatuses of the second type are constructed to read information recorded on the magnetic tape in digital form and in analog form and in that the information in digital form is arranged in a plurality of tracks and is encoded in such a way that the information in digital form can be read with the same tape-transport speed as used for reading information in analog form.

10. A system as claimed in any one of the preceding Claims 3 to 9, characterized in that the pattern of transmission gaps of the magnetic head of the second type comprises nine gaps, of which one gap forms an auxiliary gap for reading and/or writing auxiliary information and the other eight gaps form main gaps for reading and/or writing the information.

11. A magnetic tape apparatus of the second type for use in a system as claimed in any one of the preceding Claims.

12. A magnetic tape apparatus as claimed in Claim 11, characterized in that the magnetic head means of the second type comprise a magnetic head of the second type, which magnetic head is constructed to read both information in analog form and information in digital form, and which magnetic-head means comprise a further magnetic head of the second type for recording information at least in digital form.

13. A magnetic-tape apparatus as claimed in Claim 11, characterized in that the magnetic head of the second type is constructed to read and write information in digital form and at least to read information in analog form.

14. A magnetic-tape apparatus as claimed in Claim 12 or 13, characterized in that the magnetic head, which is constructed at least to read both information in analog form and information in digital form,comprises a plurality of parallel transmission gaps disposed in line with each other in a head face, which gaps are arranged in two sub-patterns, the first sub-pattern corresponding to a pattern of transmission gaps for at least reading information in digital form on the magnetic tape in one direction of tape transport, and the second sub-pattern corresponding to a pattern of transmission gaps for at least reading information in analog form on the magnetic tape in one direction of tape transport.

15. A magnetic-tape apparatus as claimed in any one of the preceding Claims 12, 13 or 14, characterized in that at least one magnetic head of the second type is rotatable through at least substantially 180^o about an axis perpendicular to the head face.

16. A magnetic-tape apparatus as claimed in any one of the preceding Claims 12, 13, 14 or 15, characterized in that at least one magnetic head of the second type is movable over a distance in a direction at least substantially parallel to the transmission gaps, which distance is at least substantially equal to half the distance between the centres of two adjacent transmission gaps, to read and/or write information in digital form on the magnetic tape in the same direction of tape transport.

17. A magnetic head of the second type, for use in a magnetic-tape apparatus as claimed in any one of the preceding Claims 12 to 16.

18. A magnetic head as claimed in Claim 17, characterized in that the magnetic head comprises eleven parallel transmission gaps of different dimensions, which gaps are disposed in line with one another in a head face, which head face is bisected by a central line perpendicular to the transmission gaps, nine of said transmission gaps being configured to read and/or write information in digital form and two further of said transmission gaps being configured to at least read information in analog form, nine transmission gaps for reading and/or writing information in digital form being provided in one half of the head face, the transmission gap which is remotest from the central line being configured to read and/or write auxiliary information in digital form, and the two transmission gaps for at least reading information in analog form being provided in the other half of the head face.

19. A magnetic head as claimed in Claim 17, characterized in that the magnetic head comprises two groups of parallel transmission gaps which are disposed in line with each other in a head face which is bisected by a central line perpendicular to the transmission gaps, which groups each comprise two subgroups, being a first subgroup having transmission gaps in one half of the head face, for reading and/or writing information in digital form and a second subgroup having transmission gaps in the other half of the head face for at least reading information in analog form, a first subgroup of one of the groups and a second subgroup of the other group of transmission gaps being provided in each half of the head face.